Lakeside53's --361 muffler mod w/photos

[forcedintoit]

I just ordered my muffler from scott wojo and he sent me the pic today. Can't wait for it to get here!

 

[SawTroll]

Yep, that's what several saw builders use, they mostly weld them on from what I've seen. The one I had didn't like the screen though, broke it off and spat it out.

Ian

Sounds like a sensible saw!

Joke aside, I think it was a good move to make this thread a sticky!

 

[Haywire Haywood]

I just ordered my muffler from scott wojo and he sent me the pic today. Can't wait for it to get here!

Doesn't look like he left you enough pipe to clip the screen on.

Ian

 

[forcedintoit]

The screen is on the inside

Doesn't look like he left you enough pipe to clip the screen on.

Ian

 

[Haywire Haywood]

Ah, then it's not a Lakeside mod....

Ian

 

[njforestfire]

Ok you saw tech's, what's your opinion?

2 Strokes do rely on backpressure on the exhaust side to run properly. If they didn't require it then why are there tune pipes on go-karts and dirt bikes and hot saws?!?!?! With this said, my muffler mods are at 80% of the exhaust port area from the jug. Run GREAT! I have read earlier in this long post about numbers from 85% to 120% of the port opening...which to me would be WAY too big to supply any backpressure. Has anyone done any studies or testing of different size openings to find what might be the optimum size? Of course one would need a base line test saw and consistantly document all changes and performance readings.

 

[ezs]

I agree with you about a Tuned System. It also is true that an expansion chamber is key in 2 stroke performance, not a baffled exhaust. So a simple hole may do something, but not like an open chamber to become a pipe. Maybe a large exit is for that restraining system in the first place? :monkey:

 

[bigjake]

anyone in the northern cincinnati area i have 2 metal lathes a small mill a tig
welder with hi frec .I do alot of metal fab so if anyone needs help or use of
the shop let me know i didnt relize how simple this was .Dam now i wish i
had a 460 instead of a 441 .Would a muffler mode work on the small saws
like a 025 .or is it for pro saws .

 

[Haywire Haywood]

Should work with any saw, just have to adjust the size of the extra port to the size of the engine.

Ian

 

[biggenius29]

I just got a 460 a month or so ago and am wanting to do a muffler mod on it, I am awful at math, so what size hole should I put in the muffler for the 85%, or would this saw be better with a 100-125% hole?

 

[Lakeside53]

Easier to just buy the factory dual port muffler front.

 

[Lakeside53]

Some guys state that the exhaust port should be 80% of the surface area on the cylinder head port. The question is what should it be with the increased back pressure of a spark arrestor screen?

If it's a stihl the screen has little effect - it's many times the area of the outlet.

 

[psych038]

All this muffler mod talk is making want to tinker with my 028. Before I start should I cut out the internal cage baffle or just drill bigger holes in it?

Also it seems some you like to take out the mesh screens and some of you strive to keep them. What's the best approch with the screens?

i took the muffler of my 028 wb last night and it has very little baffle no sceens and a huge hole.. not gunna touch it that thing already screams.
did some work to my 038 super and dont think i did enough. maybe ran a little better but not the difference everyone is talking about. i think i'm gunna open the baffles up some more... maybe cut the one after the sceen and before the exit port all the way out. maybe the sceen is chocking it?? i put my extra holes in the same area as the stock port because ther was already a sceen there. muffler is the single port 038 unit. scared of f'ing it up.

 

[MnSam]

i took the muffler of my 028 wb last night and it has very little baffle no sceens and a huge hole.. not gunna touch it that thing already screams.
did some work to my 038 super and dont think i did enough. maybe ran a little better but not the difference everyone is talking about. i think i'm gunna open the baffles up some more... maybe cut the one after the sceen and before the exit port all the way out. maybe the sceen is chocking it?? i put my extra holes in the same area as the stock port because ther was already a sceen there. muffler is the single port 038 unit. scared of f'ing it up.

After picking up on this thread and reading it through, I was thinking the same exact thing as you as far as modding my 028WB exhaust. Went out into the garage (10 degrees but it didn't matter) and took the muffler apart. I saw the same as you, no baffles and already plenty of flow. I read part way into the thread that the older saws will not benefit much from a muffler mod because of this. And like yours mine already screams. I am now looking for a good priced used "experimental" saw solely for testing purposes.

 

[warlock1944]

Flow Calculations

10 small holes of the same area as one big hole will flow less because restrition to flow is highest along the edge of an orfice, more small holes has a longer edge than one big hole of the same area.

However scavenging can be affected by too big of a single direct opening allowing fresh charge to escape the confines of the muffler, so in a way smaller openings cold be incorporated to minimize losses, but it is going to be complicated as how much of the fresh charge gets out into the muffler and how much gets sucked back into the motor depends essentially on the scavenging efficiency and design of the saw, how dilluted the escaping fresh charge becomes after entering the muffler depends on the shape and design of the muffler. Realy need to look at the flow and mixing of charge and exhaust in the muffler. The more the fresh charge dillutes into the exhaust, the less can be recouped. Run a saw with no muffler at all, and it has less power than with a typical muffler as too much charge is being lost to the suroundings and not recovered during scavenging.

The area of 10 small holes will need to have a greater area than one big hole to give the same flow and back pressure.

A measure of the flow capability (flow less than supersonic) is the hydraulic radius which is the wet perimeter / flow area. To make them approximately equal in flow characteristics set up a proportion :

wet perimeter(1)/area(1) = wet perimeter(2)/area(2) and solve for the one you want.

Very easy if you set up an excel sheet you can play what if until you get the the number and size holes that works best.

 

[timberwolf]

Yes that sounds good on paper, but flow bench tells otherwise. And even then a flow bench is steady state which still does not fully model the more dynamic real world where pressure and temperature, density and velocity are swinging all over the place 200 times a second.

What I am saying it there is more to the ideal outlet size than one would think. And I have doubts about the wet perimiter theory as far as practicle application to an exhaust outlet port.

 

[MnSam]

I'm guessing there aren't too many, if any, pictures of a Wild Thing on this site. So I'll throw this in here (with a Stihl in the background for support). I was just practicing the muffler mod concept on this before I attacked anything important. I haven't started it up yet, too late at night for the neighbors. They say you can't polish a turd, but I'm trying. Oh, and disregard the welded portion at the bottom/center portion of the muffler, I was going to cut-out there but moved it.

 

[limelakephoto]

That wild thing looks not to bad ! Nice work. I opened the muffler on my worn out 12 year old poulan and adjusted the carb and it is ready for another 12 years, now it has more snot then when i bought it.

 

[injun joe]

I read somewhere online recently that you could braze with MAPP gas. So I bought a bottle of that and a general purpose 1/8" brazing rod with the flux coating. I had my doubts about it getting hot enough, so the first thing I did was see if it would melt the rod. It melted the flux off and that was all it did. $10 gone to waste on that effort.

Ian

well i have put it my fair share of welding and i can't figure out why you couldn't braze this mapp gas burns a little less than acetylene and acetylene burns at 6000 degrees it could have been a lot of things wrong brazing rod improper hose pressure wrong size tip the list is endless.

 

[warlock1944]

wet perimeter

Yes that sounds good on paper, but flow bench tells otherwise. And even then a flow bench is steady state which still does not fully model the more dynamic real world where pressure and temperature, density and velocity are swinging all over the place 200 times a second.

What I am saying it there is more to the ideal outlet size than one would think. And I have doubts about the wet perimeter theory as far as practicle application to an exhaust outlet port.

Hydraulic Radius does indeed work as far as equating one tube size to another as long as the flow is sub sonic where the Reynolds number is linear. I did not offer anything about a percentage size for the flow area.

Two stroke tuning utilizes the exhaust standing wave to scavenge the combustion chamber allowing more charge and better efficiency. Reducing the backpressure (better flow) can in some cases (depending on port timing) hinder power output or more likely change the point at which peak power is made. This is why hot saws and ringy ding bikes have expansion chambers.

The knowledge is out there to calculate all of these factors but in today's world they do not, after all the cheapest silence is is the Idaho silencer which is why opening up mufflers works in most cases.